Prtty much nobody would understand the connotations of Locke, Mill or Hobbes, and amongst those who do they'd be contentious.
Consider that for example Mill thought despotism could be acceptable under utilitarian principles if the end result was a better society afterwards; I don't know what you think of Marx [Marx Mail? Maybe not], but even an authoritarian reading of Marx ideological works fits within utilitarian principles to those who agree with it, while those who read Marx from a libertarian viewpoint, e.g. left communists, would generally find Mills distastefully authoritarian.
Locke was a major investor in the slave trade, and a central participant in trying to institute a feudal aristocracy in Carolina - writing about freedoms while trying to deprive others of them. Locke Mail in that respect would be fitting brand for a NSA run mail service for its hypocrisy alone.
Hobbes, while talking about individual rights, was a supporter of a strong central government an a supporter of absolute monarchy. He too would be a suitable beacon for the NSA.
That is not to say that these people were not important for the development of philosophical ideas related to freedom, but only in relation to the politics of the time. Today all three of them are archaic and authoritarian compared to a lot of more recent philosophers.
As for Liberty Mail, outside of the US at least it would be likely to leave a bad taste with a lot of people. It reads like Far-Right-Wing-US-Nationalistic-Nutjob-Mail or Lets-Pretend-It-Is-Liberty-While-We-Screw-You-Over-Mail to me, and I know a lot of people likely to have similar reactions.